Method of allocating resource region to reduce map overhead

ABSTRACT

A method of allocating a radio resource in a wireless access system is disclosed. The method includes receiving a control message associated with radio resource allocation for transmitting uplink data to the base station, wherein the control message comprises a first persistent uplink allocation information element comprising first resource allocation information associated with a first resource allocation region for transmitting the uplink data of a mobile station and transmitting an acknowledgment (ACK) message from the mobile station to the base station in response to successfully receiving the first persistent uplink allocation information element.

CROSS-REFERENCE TO RELATED APPLICATIONS

Pursuant to 35 U.S.C. §119(a), this application claims the benefit ofearlier filing date and right of priority to Korean Application No.10-2007-0095946, filed on Sep. 20, 2007, the contents of which arehereby incorporated by reference herein in their entirety.

FIELD OF THE INVENTION

The present invention relates to a wireless access system, and moreparticularly to a packet transmission method for frequent packettransmission and a method of allocating radio resources in the wirelesscommunication system.

DESCRIPTION OF THE RELATED ART

A broadband wireless access system to transmit a packet to userequipment (UE) based on an IP-based Voice over Internet Protocol (VoIP)service is described below. VoIP traffic is created with a fixed sizehaving a fixed period within a VoIP codec. VoIP communication may beclassified into a talk-spurt period and a silence period. During thetalk-spurt period, a speech mode is maintained between users. During thesilence period, the user listens to the other party without talking tothe other party. The silence period may occupy 50% or more of a generalcall session.

Therefore, in order to allocate different amounts of bandwidths to thetalk-spurt period and the silence period, a variety of voice codecs maybe used. A representative example of the voice codec is an adaptivemulti-rate (AMR) for use in a Global System for Mobile communication(GSM) and a Universal Mobile Telecommunications System (UMTS).

Voice data is not generated during the silence period. If the bandwidthis allocated to the silence period, radio resources may be wasted. Inorder to prevent this problem, VoIP supports a silence suppressionscheme. According to the silence suppression scheme, a vocoder forgenerating the VoIP traffic does not generate traffic data. However, thevocoder periodically generates comfort noise to inform the other userthat the call is still ongoing. For example, the vocoder based on theabove-mentioned AMR codec generates a fixed-sized packet at intervals of20 ms in the talk-spurt period, and generates the comfort noise atintervals of 160 ms in the silence period.

In order to perform resource allocation of traffic data, which has afixed-sized constant period such as a VoIP, a Node-B or base station(BS) may fixedly assign a predetermined region to a specific UE. Forexample, the BS assigns the region as large as the initially-definedsize to the UE capable of supporting the VoIP service. The BS may alsoinform the UE of the assigned resource region information using acontrol channel or a control message such as a UL-MAP or a DL-MAP.Accordingly, the control channel or the control message, which isinitially transmitted, may also include period information of the nextallocation region.

From the next period, the BS may successively assign a correspondingregion without any specified notification associated with the aboveregion which has been notified to the mobile station (MS), using theinitially-transmitted control channel or the initially-transmittedcontrol message. Therefore, the MS transmits the VoIP packet to theassigned region using region information which has been initiallyassigned on the map and transmits the VoIP packet from the next periodto the same region using period information.

For example, when the frame length is set to 5 ms in consideration ofthe VoIP service and a frame period assigned to the MS for VoIP packettransmission is set to 4 frames, the frame period assigned to the MS forthe VoIP packet transmission may be changed to another according toservice characteristics. Specifically, if the same VoIP service is used,the frame period assigned for VoIP packet transmission may be defined indifferent ways according to individual elements such as systemcharacteristic and VoIP service status. For example, the systemcharacteristic may be changed according to the frame length and the VoIPservice status may be either the talk-spurt period or the silenceperiod.

The BS located at an initial frame informs the MS of the allocationregion information to transmit the VoIP packet via the UL-MAP. If the BSis located at a fourth or eighth frame corresponding to each period, itdoes not inform the region information via the UL-MAP and assigns onlythe region for VoIP packet transmission. In this case, the periodassigned for the VoIP packet transmission may be 4 frames or 20 ms.

The MS stores region allocation information contained in the UL-MAPmessage received from the initial frame. Therefore, the MS can transmitthe VoIP packet via a corresponding region although the UL-MAP messageis not additionally received from the fourth and eighth framescorresponding to the resource allocation period. Accordingly, the BS isfixed to a single VoIP connection due to the VoIP traffic characteristicand can persistently assign resources to this VoIP connection.

If a control message for assigning a new transmission region is lost ina wired or wireless downlink, the conventional system has a disadvantagein that individual transmission region information recognized by the MSand the BS is unavoidably different from each other. Therefore, in caseof the downlink, the MS is unable to receive the VoIP packet from theBS.

In case of the uplink, although the MS transmits the VoIP packet via thesecond transmission region, the BS may assign the second transmissionregion to another MS, resulting in unexpected problems. In other words,if the MS transmits the VoIP packet via the second transmission region,a packet transmission by another MS may fail. If the system uses anincremental redundancy (HARQ-IR) scheme, the number of retransmissionwill be increased, resulting in unexpected problems.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a packet transmissionmethod for resource allocation in a broadband wireless access systemthat substantially obviates one or more problems due to limitations anddisadvantages of the related art. An object of the present invention isto provide a method for assigning a resource region and a controlchannel to provide the MS with persistent service. Another object of thepresent invention is to provide a method for solving the problemsencountered when the MS does not receive the control message forassigning the radio resources.

Another object of the present invention is to provide a method forreassigning the transmission region when the MS does not receive thecontrol message for assigning the VoIP packet transmission region duringthe UL/DL VoIP packet transmission. Yet another object of the presentinvention is to provide a method for solving the problems encounteredwhen the radio resources for VoIP packet transmission/reception areassigned, modified, and deleted.

The present invention has been devised to solve the above-mentionedobjects. According to an embodiment of the present invention, a methodof allocating a radio resource in a wireless access system is provided.The method includes receiving a control message associated with radioresource allocation for transmitting uplink data to the BS, wherein thecontrol message comprises a first persistent uplink allocationinformation element comprising first resource allocation informationassociated with a first resource allocation region for transmitting theuplink data of the MS and transmitting an acknowledgment (ACK) messagefrom the MS to the BS in response to successfully receiving the firstpersistent uplink allocation information element.

In an aspect of the present invention, the method further includestransmitting the uplink data to the BS by the MS via the assigned firstresource allocation region. If the ACK message is not received from theMS, the first persistent allocation information element isretransmitted. Preferably, the retransmission of the first persistentallocation information element occurs after a predetermined number offrames after not receiving the ACK message. Preferably, a payload sizeof the uplink data is fixed and the uplink data includes an IP-basedVoice over Internet Protocol (VoIP) data.

In another aspect of the present invention, the first resourceallocation information comprises at least one of orthogonal frequencydivision mulitiplxing access (OFDMA) symbol offset, subchannel offset,and information of OFDMA slot. Besides, the first persistent uplinkallocation information element further comprises first ACK informationassociated with ACK transmission region, and the ACK message istransmitted via an ACK transmission region which is indicated by thefirst ACK information.

In another aspect of the present invention, the first persistent uplinkallocation information element further comprises a field for indicatingwhether the first resource allocation region is allocated orde-allocated.

In another aspect of the present invention, the method also includesstoring the first persistent uplink allocation information element inthe MS. The method may further include receiving a second persistentuplink allocation information element comprising second resourceallocation information associated with a second resource allocationregion for transmitting the uplink data. Furthermore, the method mayinclude storing the second persistent uplink allocation informationelement and transmitting an acknowledgment (ACK) signal from the MS tothe BS in response to successfully receiving the second persistentuplink allocation information element.

The method may include transmitting the uplink data to the BS via theassigned second resource allocation region. The MS continuestransmitting the uplink data to the BS via the first resource allocationregion until a second persistent uplink allocation information elementassociated with using a second resource allocation region is received.In the other aspect of present invention, the second persistent uplinkallocation information element further comprises second ACK informationassociated with ACK transmission region, and the ACK message istransmitted via an ACK transmission region which is indicated by thesecond ACK information.

According to an embodiment of the present invention, the method ofallocating a radio resource in a wireless access system includesreceiving a control message associated with radio resource allocationfor receiving downlink data from the BS, wherein the control messagecomprises a first persistent downlink allocation information elementcomprising first resource allocation information associated with a firstresource allocation region for receiving the downlink data from the BSand transmitting an acknowledgment (ACK) message from the MS to the BSin response to successfully receiving the first persistent downlinkallocation information element.

In an aspect of the present invention, the method further includesreceiving the downlink data from the BS via the assigned first resourceallocation region. Preferably, a payload size of the downlink data isfixed.

In another aspect of the present invention, the method further includesreceiving a second persistent downlink allocation information elementincluding second resource allocation information associated with asecond resource allocation region for receiving downlink data. Themethod may further include storing the second persistent downlinkallocation information element and transmitting an acknowledgment (ACK)signal from the MS to the BS in response to successfully receiving thesecond persistent downlink allocation information element.

The method may also include receiving the downlink data from the BS viathe assigned second resource allocation region. The MS continuesreceiving the downlink data from the BS via the first resourceallocation region until a second persistent downlink allocationinformation element associated with using a second resource allocationregion is received. The first resource persistent downlink allocationinformation may comprise at least one of OFDMA symbol offset, subchanneloffset, and information of OFDMA slot.

According to an embodiment of the present invention, the method ofallocating a radio resource in a wireless access system includestransmitting a control message associated with radio resource allocationfor communicating data to the MS, wherein the control message comprisesa first persistent allocation information element comprising firstresource allocation information associated with a first resourceallocation region for communicating the data and receiving anacknowledgment (ACK) message from the MS in response to successfullyreceiving the first persistent allocation information element. Themethod may further include communicating the data via the assigned firstresource allocation region. Preferably, a payload size of the data isfixed.

In an aspect of the present invention, the method further includestransmitting a second persistent allocation information elementincluding second resource allocation information associated with asecond resource allocation region for communicating the data. The methodmay further include storing the second persistent allocation informationelement and receiving an acknowledgment (ACK) signal from the MS inresponse to successfully receiving the second persistent allocationinformation element.

In another aspect of the present invention, the method may also includetransmitting the data to the MS via the assigned second resourceallocation region. The BS continues receiving the data from the MS viathe first resource allocation region until a second persistentallocation information element associated with using a second resourceallocation region is received by the MS.

In the other aspect of the present invention, the first persistentallocation information element further comprises ACK transmission regionallocation information, and the ACK message is received via an ACKtransmission region which is indicated by the ACK transmission regionallocation information. At this time, the first persistent uplinkallocation information further comprises a field for indicating whetherthe first resource allocation region is allocated or de-allocated.Moreover, the first resource persistent downlink allocation informationcomprises at least one of OFDMA symbol offset, subchannel offset, andinformation of OFDMA slot.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention, illustrate embodiments of the inventionand together with the description serve to explain the principle of theinvention.

FIG. 1 is a flow chart illustrating a BS assigning fixed radio resourcesto a MS using a MAP message in an uplink.

FIG. 2 is a flow chart illustrating the BS assigning fixed radioresources to the MS using the MAP message in a downlink.

FIG. 3 is a flow chart illustrating assignment of a radio-resourceregion to provide the VoIP service according to an embodiment of thepresent invention.

FIG. 4 is a flow chart illustrating transmission of a VoIP-associatedMAP message in an uplink according to an embodiment of the presentinvention.

FIG. 5 is a flow chart illustrating transmission of a VoIP-associatedMAP message in a downlink according to an embodiment of the presentinvention.

FIG. 6 is a flow chart illustrating retransmission of a VoIP-associatedMAP message in an uplink according to an embodiment of the presentinvention.

FIG. 7 is a flow chart illustrating retransmission of a VoIP-associatedMAP message in a downlink according to an embodiment of the presentinvention.

FIG. 8 is a flow chart illustrating retransmission of a VoIP-associatedMAP message in an uplink according to an embodiment of the presentinvention.

FIG. 9 is a flow chart illustrating retransmission of a VoIP-associatedMAP message in a downlink according to an embodiment of the presentinvention.

FIG. 10 is a flow chart illustrating retransmission of a VoIP-associatedcontrol message in an uplink according to an embodiment of the presentinvention.

FIG. 11 is a flow chart illustrating retransmission of a VoIP-associatedcontrol message in a downlink according to an embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following detailed description, reference is made to theaccompanying drawing figures which form a part hereof, and which show byway of illustration specific embodiments of the invention. It is to beunderstood by those of ordinary skill in this technological field thatother embodiments may be utilized, and structural, electrical, as wellas procedural changes may be made without departing from the scope ofthe present invention. Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or similarparts.

Prior to describing the present invention, it should be noted that mostterms disclosed in the present invention correspond to general termswell known in the art, but some terms have been selected by theapplicant as necessary and will hereinafter be disclosed in thefollowing description of the present invention. Therefore, it ispreferable that the terms defined by the applicant be understood on thebasis of their meanings in the present invention.

The present invention relates to a wireless access system. In moredetail, the present invention provides the packet transmission methodwhen the packet is frequently transmitted and a method of assigningradio resources in the wireless access system.

The order of operations disclosed in the embodiments of the presentinvention may be changed. Some components or characteristics of anyembodiment may also be included in other embodiments, or may be replacedwith those of other embodiments as necessary.

The following embodiments of the present invention will be disclosed onthe basis of a data communication relationship between the BS and theMS. The BS is used as a terminal node of a network via which the BS candirectly communicate with the MS. Specific operations to be conducted bythe MS in the present invention may also be conducted by an upper nodeof the BS as necessary. Various operations for enabling the BS tocommunicate with the MS in a network composed of several network nodesincluding the BS may be conducted by the BS or other network nodes otherthan the BS.

The base station (BS) may also be called as a fixed station, Node-B,eNode-B (eNB), or an access point as necessary. The mobile station (MS)may also be called as a user equipment (UE) or a mobile subscriberstation (MSS) as necessary.

The following embodiments of the present invention will disclose theVoIP service as an exemplary service which requires frequent packettransmission. However, it should be noted that the present invention isnot limited to the VoIP service and can also be applied to otherservices requesting frequent packet transmission/reception. A packettransmission method for VoIP and the resource allocation method for thesame VoIP under the condition that the packet transmission is frequentlyrequired will be described hereinafter.

FIG. 1 shows an uplink case in which the MS transmits the VoIP packet tothe BS. Referring to FIG. 1, the MS and the BS determine whether theresource allocation method is made available while the VoIP service isgenerated in S101.

If it is determined that the resource allocation is made available inS101, the BS includes “VoIP_UL_IE” in the UL-MAP message and assigns theradio transmission region for providing the VoIP service in S102. TheUL-MAP message is used as a control message and includes a radiotransmission region which enables the MS to transmit the VoIP packet tothe BS. The BS assigns a first transmission region to the MS via theUL-MAP message.

When the MS receives the UL-MAP message from the BS, the MS storesallocation information for the first transmission region included in theUL-MAP message in S103. Subsequently, the MS transmits the VoIP packetto the BS via the first transmission region which has been assigned fromthe BS in S104.

In order to assign the traffic resources having a fixed-sized constantperiod, such as the VoIP packet, the BS fixedly assigns a firsttransmission region to the MS in S102. Therefore, the BS cancontinuously assign the first transmission region to the MS withoutnotifying other messages via an initial transmission control channel oran initial transmission control message.

The VoIP packet is transmitted at intervals of a predetermined time,such that the MS goes to the next period, for example, a lapse of 20 ms,and transmits the next VoIP packet to the BS via the first transmissionregion in S105. While the MS transmits/receives the VoIP service to/fromthe BS, channel environments or data transmission environments may beunexpectedly deteriorated and it may be difficult to implement packettransmission/reception via the first transmission region. Therefore, theBS includes “VoIP_UL_IE” in the control message “UL-MAP” and assigns asecond transmission region to the MS. In this case, the secondtransmission region is assigned to a specific location different fromthat of the first transmission region in S106.

When the MS receives the above mentioned UL-MAP message in S106, thefirst transmission region for the VoIP service is updated with thesecond transmission region included in the UL-MAP message in S107.Subsequently, the MS transmits the VoIP packet to the BS via the secondtransmission region in S108.

The BS receiving the VoIP packet via the second transmission region mayneed to change a current transmission region to another transmissionregion, if necessary. Therefore, in order to assign a third transmissionregion that is different from the second transmission region to the MS,the BS transmits the UL-MAP message including “VoIP_UL_IE” to the MS inS109.

However, the UL-MAP message may be lost during wired or wirelesstransmission in S109 such that the MS does not receive the UL-MAPmessage. Alternatively, although the MS receives the UL-MAP message, itmay be unable to detect the UL-MAP message due to the faulty orerroneous operation of the UL-MAP message.

In this case, the MS is unable to recognize the information of the thirdtransmission region in S109 and transmits the VoIP packet to the BSusing the previous information, for example, information of the secondtransmission region for the next period in S110. Therefore, if the BSassigns the second transmission region for the VoIP service of anotherMS in S110, at least two MSs transmit the VoIP packet to the same secondtransmission region. As a result, packets may collide with each otherand the BS may not receive such packets. Further, the BS does notreceive the packet via the third transmission region assigned to the MSand is unable to receive the packet normally from the MS.

Referring to FIG. 2, it is noted that S201˜S203 of FIG. 2 are similar toS101˜S103 of FIG. 1. In other words, in a downlink, the BS transmits thefirst transmission region to the MS using the DL-MAP message acting asthe control message in S202. The MS stores allocation information of thefirst transmission region in S203 and is ready to receive the VoIPpacket from the BS.

The BS transmits the VoIP packet to the MS via the first transmissionregion in S204. In this case, in order to assign radio resources fortraffic, such as VoIP packet, having a fixed-sized period, the BSfixedly assigns the first transmission region to the MS in S202.Therefore, the BS can continuously assign the transmission region to theMS without notifying other messages via an initial transmission controlchannel or an initial transmission control message.

The VoIP packet is transmitted at intervals of a predetermined time suchthat the BS goes to the next period, for example, a lapse of 20 ms, andtransmits the next VoIP packet to the MS via the first transmissionregion in S205. While the MS transmits/receives the VoIP service to/fromthe BS, channel environments or data transmission environments may beunexpectedly deteriorated and it may be difficult to perform packettransmission/reception via the first transmission region. In this case,the BS includes “VoIP_DL_IE” in the control message “DL-MAP” and mayassign a second transmission region that is different from the firsttransmission region to the MS in S206.

When the MS receives the above mentioned DL-MAP message in S206, thesecond transmission region contained in the DL-MAP message is updated inS207. The BS transmits the VoIP packet to the MS via the secondtransmission region assigned to the MS in S208.

The BS providing the VoIP service via the second transmission region mayneed to change a current VoIP packet transmission region to anothertransmission region. Therefore, in order to assign a third transmissionregion that is different from the second transmission region, the BStransmits the DL-MAP message including “VoIP_DL_IE” to the MS in S209.

However, the DL-MAP message may be lost during wired or wirelesstransmission in S209 and the MS may not receive the DL-MAP message.Alternatively, although the MS receives the DL-MAP message, it may beunable to detect the DL-MAP message due to the faulty or erroneousoperation of the DL-MAP message.

In this case, the MS is unable to receive the DL-MAP message normally inS209 and unable to recognize information of the third transmissionregion. Therefore, the BS continues to transmit the VoIP packetperiodically to the MS via the second transmission region and the MS isunable to receive the VoIP packet via the third transmission region.

FIGS. 1 and 2 show that the BS assigns the resource region to the MSusing the control message “MAP IE”. However, when the MS receives theMAP IE message abnormally and the BS changes a transmission region forthe VoIP service to another region, an unexpected problem may ariseduring packet transmission because the MS and the BS have information ofdifferent transmission regions.

Referring to FIG. 3, a VoIP service is generated between the MS and theBS in S301. The BS and the MS negotiate with each other about thepersistent resource allocation method used when the VoIP service isgenerated in S301. According to an embodiment of the present invention,the persistent resource allocation is available or the persistentallocation is enabled.

The BS assigns the first transmission region to transmit/receive theVoIP packet to/from the MS using the control message such as the MAPmessage in S302. The BS transmits/receives the VoIP packet to/from theMS via the first transmission region. In other words, in the uplink, theMS transmits the VoIP packet to the BS via the first transmission regionand in the downlink, the BS transmits the VoIP packet to the MS via thefirst transmission region.

While the BS transmits the VoIP service to the MS, user environment maybe changed or communication quality may be deteriorated. In this case,the BS determines to change a packet transmission region for the VoIPservice in S303.

The BS assigns the changed second transmission region to the MS. The BStransmits or receives the VoIP service to/from the MS via the secondtransmission region in S304.

The BS may use the control message in order to assign the secondtransmission region to the MS in S304. A message characterized by itssolidity is used as the control message which includes a MAP message.The MAP message (DL-MAP/UL-MAP) is used to assign unique resource foreach user. This MAP message is a MAC management message whichdynamically informs the MS of the resource allocation result atintervals of each frame.

In the downlink, the UL-MAP message designates the location ofsub-channel dynamically assigned to each MS and the number of thesub-channel. In the uplink, the DL-MAP message designates the locationof sub-channel dynamically assigned to each MS and the number of thesub-channel. In particular, the DL-MAP message is a broadcast messagewhich indicates the set of information associated with total connectionmanaged by a single BS. For example, the DL-MAP message may include theprincipal information, band allocation information, frame constructioninformation, and ACK/NACK information.

The following table 1 shows an example of the VoIP UL-MAP informationelement (VoIP_UL_IE) which may be used to perform resource allocation,modify the resource allocation, and de-allocation the same.

TABLE 1 Syntax Size Note VoIP_UL_IE( ){ — — Extended UIUC 4 bits VoIP_UL= 0x06 Length 4 bits Variable Type 2 bits 0b00 = Initial allocation 0b01= parameter modification 0b10 = de-allocation 0b11 = reservation If(type== 0b00 ) { — — UIUC 4 bits UIUC for transmission OFDMA symbol offset 8bits Subchannel offset 8 bits Duration 4 bits OFDMA slot unit Period(P)4 bits BS performs resource allocation using offsets contained in IE andthe duration at intervals of 2^(P) frame Repetition coding indication 2bits 0b00 - disuse of repetition code 0b01 - use of repetition code 20b10 - use of repetition code 4 0b11 - use of repetition code 6 } elseif( type == 0b01 ){ — — Change type 2 bits 0b00 - modification of onlyslot offset 0b01 - modification of only duration 0b10 - modification offrame offset 0b11 - modification of duration, period, and repetitioncoding If( change type == 0b00) { — — OFDMA symbol offset 8 bitsSubchannel offset 8 bits } else if( change type == 0b01 ) { — — UIUC 4bits UIUC for transmission Duration 4 bits OFDMA slot unit Repetitioncoding indication 2 bits 0b00 - disuse of repetition code 0b01 - use ofrepetition code 2 0b10 - use of repetition code 4 0b11 - use ofrepetition code 6 } else if( change type == 0b10 ){ — — UIUC 4 bits UIUCfor transmission Frame offset (S) 6 bits Base station (BS) will performthe resource allocation after the lapse of S frame from a current frameOFDMA symbol offset 8 bits — Subchannel offset 8 bits — Duration 4 bitsOFDMA slot unit Repetition coding indication 2 bits 0b00 - disuse ofrepetition code 0b01 - use of repetition code 2 0b10 - use of repetitioncode 4 0b11 - use of repetition code 6 Mode Indication 1 bits 0b0 -resource allocation maintenance in current frame 0b1 - resourcede-allocation in current frame } else { — — UIUC 4 bits UIUC fortransmission Duration 4 bits OFDMA slot unit Period 4 bits Repetitioncoding indication 2 bits 0b00 - disuse of repetition code 0b01 - use ofrepetition code 2 0b10 - use of repetition code 4 0b11 - use ofrepetition code 6 } — — } else if( type == 0b10 ) { — — — — } — —Padding variable The number of bits to be adjusted to the byte length.The number of bits may be set to 0 } — —

Referring back to FIG. 3, in order to assign the second transmissionregion, the BS transmits the control message to the MS in S304. In thiscase, the MS receives the control message and can recognize the secondtransmission region in S305. If the MS receives the control message andrecognizes the second transmission region (‘Yes’ in S305), it transmitsor receives the VoIP packet to/from the BS via the second transmissionregion in S306.

The MS may not receive the control message in S305 (‘No’) due to a lossof the control message during wired or wireless transmission. Or, evenif the control message is received by the MS, it may not be recognizeddue to errors in the control message. In this case, the BS reallocatesthe second transmission region to the MS using a specific algorithm inS307. This step may be repeated until the second transmission regionequal to a new transmission region is recognized. The number ofrepetition may be determined according to the communication environmentand a system requirement.

In order to reallocate the second transmission region, a variety ofalgorithms may be used in S307. According to one of various algorithms,if a control message for allocating the second transmission region isreceived normally, an acknowledgment (ACK) signal for the controlmessage is transmitted to the BS such that the MS indicates that thesecond transmission region has been normally recognized.

If the MS does not receive the control message normally, it is unable totransmit the ACK signal. Provided that the BS transmits the controlmessage for assigning the transmission region and does not receive theACK signal from the MS, it may retransmit the above-mentioned controlmessage after a lapse of a predetermined number of frames, for example,N frames, in the next frame or system.

According to another algorithm, the BS determines the presence orabsence of a signal of the second transmission region in S307 such thatit may reallocate the second transmission region. In this case, the BSdoes not use the ACK signal and determines whether the signal istransmitted from the MS to the second transmission region. Further,other types of algorithms may also be used to assign the secondtransmission region.

According to an embodiment of the present invention, a method for usingthe ACK signal to reply to the control message, which can allocation,modify, or de-allocation radio resources for the VoIP service, isdescribed below. If the MS receives the VoIP-associated MAP IE messagefrom the BS when the MAP IE message, such as VoIP_DL_IE VoIP_UL_IE, isused as a control message, the MS may transmit the ACK signal to the BSin response to the MAP IE message. In this case, the BS allocates thecontrol channel to a designated frame such that the MS can transmit theACK signal.

The ACK signal transmitted from the MS to the BS in response to thecontrol message may be an ACK/NACK or ACK message of a Hybid AutomaticRepeat Request (HARQ), or an ACK header. If the BS does not receive theACK signal at a corresponding frame, the BS may retransmit the controlmessage, which has been transmitted to the MS, to the designated frame,or may allocate radio resources to the MS using the radio-resourceinformation pre-notified to the MS.

Referring to FIG. 4, in an uplink, the process for generating the VoIPservice between the MS and the BS and allocating the first transmissionregion is equivalent to S101˜S104 of FIG. 1. Therefore, these steps areomitted and the next steps are described in FIG. 4.

The MS transmits the VoIP packet to the BS via the first transmissionregion assigned from the BS in S401. While the VoIP packet istransmitted or received, the transmission region may need to be changedto another region due to poor communication environments or some otherreasons. In this case, the BS may allocate the second transmissionregion to the MS using the UL-MAP message (VoIP_UL_IE) acting as acontrol message in S402. Also, the BS may allocate a specific regioncapable of transmitting the ACK signal via the control message.

When the MS receives the control message from the BS, the MS updates thesecond transmission region contained in the control message to a newtransmission region in S403. When the MS has received the controlmessage normally in S402, the MS transmits the ACK signal, such as HARQ,ARK, ACK message or ACK header, to the BS in order to reply to thenormally-received control message in S404. Then, the MS transmits theVoIP packet to the BS via the second transmission region, which wasassigned as the new transmission region from the BS, in S405.

Referring to FIG. 5, in a downlink, the process for generating the VoIPservice between the MS and the BS and allocating the first transmissionregion is equivalent to S201˜S204 of FIG. 2. Therefore, the same stepsare omitted and the next steps are described in FIG. 5.

The BS transmits the VoIP packet to the MS via the first transmissionregion assigned to the MS in S501. While the VoIP packet is transmittedor received, the transmission region may need be changed to anotherregion due to poor communication environments or some other reasons. Inthis case, the BS may allocate the second transmission region to the MSusing the DL-MAP message (VoIP_DL_IE) acting as a control message inS502. Also, the BS may allocate a specific region capable oftransmitting the ACK signal via the control message.

If the MS receives the control message from the BS, the MS updates thesecond transmission region contained in the control message to a newtransmission region in S503. When the MS has received the controlmessage normally in S502, the MS can transmit the ACK signal, such asHARQ, ARK, ACK message or ACK header, to the BS in order to reply to thenormally-received control message in S504. Then, the BS transmits theVoIP packet via the second transmission region, which was assigned tothe MS as the new transmission region, in S505.

Referring to FIG. 6, in an uplink, the BS and the MS generate the VoIPservice and the BS allocates the transmission region for providing theMS with the VoIP service. The above-mentioned operations are similar toS101˜S104 of FIG. 1, and therefore, the same steps are omitted and thenext steps are described in FIG. 6.

The MS transmits the VoIP packet via the first transmission regionassigned from the BS in S601. While the BS transmits the VoIP service tothe MS, it may need to change the radio resources assigned to the MS toother radio resources. In this case, the BS allocates the secondtransmission region to the MS using the UL-MAP message (VoIP_UL_IE) usedas a control message in S602.

However, it should be noted that the control message transmitted fromthe BS to the MS may be lost or damaged during wired or wirelesstransmission, or the MS may not recognize the control message due tofaulty or erroneous operations. When the control message is lost, the MSis unable to transmit the ACK signal associated with the above-mentionedcontrol message of S602 to the BS in S603.

The BS transmits the control message in S602 and waits for the ACKsignal to determine whether the MS has recognized the secondtransmission region. However, since the MS is unable to transmit the ACKsignal in S603 because the control message has been lost, the BSdetermines that the second transmission region has not been recognizedby the MS. Therefore, the BS retransmits the UL-MAP message andreallocates the second transmission region in S604.

The BS retransmits the UL-MAP message for reallocating the secondtransmission region to the MS after a lapse of a predetermined value,for example, N frames, as determined by the next fame or system in S604.The UL-MAP message is immediately retransmitted at the next frame afterS603.

The MS recognizes the second transmission region contained in the UL-MAPmessage retransmitted from the BS and updates the first transmissionregion for VoIP-packet transmission with the second transmission regionin S605. Then, the MS transmits the ACK signal to the BS in response tothe received UL-MAP message in S606 and transmits the VoIP packet viathe second transmission region assigned from the BS. Even if the MS doesnot receive a new transmission region by the above described steps, theMS according to the present invention can quickly receive thetransmission region from the BS such that it can effectively provide theVoIP service.

Referring to FIG. 7, in a downlink, the BS and the MS generate the VoIPservice and the BS allocates the transmission region for providing theMS with the VoIP service. The above-mentioned operations are similar toS201 to S204 of FIG. 2, and therefore, the same steps are omitted andthe next steps are described in FIG. 7.

The BS transmits the VoIP packet via the first transmission regionassigned to the MS in S701. While the BS transmits the VoIP service tothe MS, the radio resources assigned to the MS may need to be changed toother radio resources. In this case, the BS allocates the secondtransmission region to the MS using the DL-MAP message (VoIP_DL_IE) usedas a control message in S702.

However, it should be noted that the control message transmitted fromthe BS to the MS may be lost or damaged during wired or wirelesstransmission in S702, or the MS may not recognize the control messagedue to faulty or erroneous operations in S702. As a result, the MS isunable to transmit the ACK signal associated with the above-mentionedcontrol message from S702 to the BS in S703.

The BS transmits the control message in S702 and waits for the ACKsignal to determine whether the MS has recognized the secondtransmission region. However, since the DL-MAP message transmitted fromthe BS has been lost in S702, the MS is unable to transmit the ACKsignal. Therefore, the BS determines that the second transmission regionhas not been recognized by the MS and retransmits the DL-MAP message toreallocate the second transmission region in S704.

The BS retransmits the DL-MAP message to reallocate the secondtransmission region to the MS after a lapse of a predetermined value,for example, N frames, determined by the next fame or system in S704.The DL-MAP message is retransmitted immediately at the next frame afterS703.

The MS recognizes the second transmission region contained in the DL-MAPmessage retransmitted from the BS and updates the first transmissionregion for VoIP-packet transmission with the second transmission regionin S705. Then, the MS transmits the ACK signal to the BS in response tothe received DL-MAP message in S706 and the BS transmits the VoIP packetto the MS via the assigned second transmission region in S707.Accordingly, even if the MS has not received a new transmission regionby the above described steps, the BS according to an embodiment of thepresent invention can quickly reallocate the transmission region toprovide the VoIP service effectively.

Referring to FIG. 8, in an uplink, the BS and the MS generate the VoIPservice and the BS allocates the transmission region for providing theMS with the VoIP service. The above-mentioned operations are similar tosteps S101˜S104 of FIG. 1, and therefore, the same steps are omitted andonly different steps are described with reference to FIG. 8.

The MS transmits the VoIP packet via the first transmission regionassigned from the BS in S801. The resource-allocation region may need tobe changed to another region during the VoIP packet communicationbetween the BS and the MS. In this case, the BS may allocate the newsecond transmission region to the MS using the UL-MAP message(VoIP_UL_IE) used as a control message in S802.

However, it should be noted that the control message transmitted fromthe BS to the MS may be lost or damaged during wired or wirelesstransmission or the MS may not recognize the control message due tofaulty or erroneous operations. When the UL-MAP message is lost in S802,the MS is unable to transmit the ACK signal via the above mentionedregion, which has been allocated to the MS for ACK signal transmission,in S803.

Since the BS has not received the ACK signal from the MS in S803, itdoes not allocate the first transmission region, which has beenpre-assigned to the MS, to either another MS or another service. Also,the BS may allocate resources to the corresponding MS using the previousinformation.

Since the MS has not received the UL-MAP message, it is unable totransmit the VoIP packet via the second transmission region. Therefore,the MS continues to transmit the VoIP packet to the BS via thepre-assigned first transmission region in S804.

When the BS receives the VoIP packet from the MS via the firsttransmission region, it determines that the control message in S802 hasnot been received normally by the MS. Specifically, even after the BSassigns the second transmission region to the MS, when the MSretransmits the VoIP packet via the first transmission region, the BSdetermines that the MS has not received the control message normally inS802.

Therefore, after a lapse of the next frame or N frames of S803, the BSretransmits the UL-MAP message (VoIP_UL_IE) to the MS to allocate thesecond transmission region in S805. When the MS has received the UL-MAPmessage normally from the BS in S805, the MS transmits the ACK signal tothe BS via a predetermined region for transmitting the ACK signalcontained in the above-mentioned UL-MAP message in S806.

Referring to FIG. 9, in a downlink, the BS and the MS generate the VoIPservice and the BS allocates the first transmission region for providingthe MS with the VoIP service. The above-mentioned operations are similarto S201˜S204 of FIG. 2, and therefore, the same steps are omitted andonly different steps are described with reference to FIG. 9.

The BS transmits the VoIP packet via the first transmission regionassigned to the MS in S901. The resource-allocation region may need tobe changed to another region during the VoIP packet communicationbetween the BS and the MS. In this case, the BS may allocate the newsecond transmission region to the MS using the DL-MAP message(VoIP_DL_IE) used as a control message in S902.

However, it should be noted that the control message transmitted fromthe BS to the MS may be lost or damaged during wired or wirelesstransmission in S902, or the control message may be received by the MSabnormally due to faulty or erroneous operations. In S902, the DL-MAPmessage has been lost, and therefore, the MS does not transmit the ACKsignal via the above described region, which has been allocated from theBS to transmit the ACK signal, in S903.

Since the BS has not received the ACK signal from the MS in S903, itdoes not allocate the first transmission region, which has beenpre-allocated to the MS, to either another MS or another service. Also,the BS allocates resources to the corresponding MS using the previousinformation.

As shown in S903, the BS has not received the ACK signal in response tothe DL-MAP message of S902. Therefore, the BS determines that the MS hasnot recognized the second transmission region yet and transmits the VoIPpacket via the first transmission region in S904.

When the BS has not received ACK signal from the MS, it determines thatthe MS has received the control message of S902 abnormally. Therefore,after a lapse of the next frame or the predetermined N frames of theS803, the BS retransmits the DL-MAP message (VoIP_DL_IE) to the MS toallocate the second transmission region in S905. When the MS hasreceived the DL-MAP message normally from the BS in S905, the MStransmits the ACK signal to the BS via a predetermined region totransmit the ACK signal contained in the above-mentioned DL-MAP messagein S906.

As described above, if the radio resources for the VoIP service areallocated according to the present invention, FIGS. 4˜9 show not only amethod for allocating radio resources between the BS and the MS usingthe ACK signal, but also a method for recovering a synchronizationfailure. According to another embodiment of the present invention, amethod is provided for determining whether there is a signal associatedwith a radio resource region assigned to the MS by the BS andretransmitting the control message according to the determined result.According to yet another embodiment, the present invention can solve theinconsistency in radio-resource-region allocation between the BS and theMS.

For example, if no signal associated with the uplink traffic is detectedas a signal of the radio-resource region which has been allocated to theMS, the BS determines that it has recognized another radio-resourceregion instead of the above radio-resource region having been assignedto the MS. Therefore, the BS retransmits the control message toreallocate the radio-resource region.

In case of a downlink, the BS transmits the packet to a specific regionpre-assigned to the MS in association with downlink traffic. However, ifno signal is detected in the radio-resource region assigned to the MS,the BS determines that the MS has information different from that of theradio-resource region allocated by the BS in association with thedownlink. Therefore, the MS retransmits the control message toreallocate the radio-resource region.

Referring to FIG. 10, in an uplink, the VoIP service is generatedbetween the MS and the BS and the BS allocates the first transmissionregion for providing the MS with the VoIP service. The above-mentionedoperations are similar to S101˜S104 of FIG. 1, and therefore, the samesteps are omitted and only different steps are described with referenceto FIG. 10.

The MS transmits the VoIP packet via the first transmission regionassigned from the BS to implement VoIP packet transmission in S1001.While the VoIP packet is transmitted or received, the transmissionregion may need to be changed to another region due to poorcommunication environments or some other reasons. In this case, the BSmay allocate the second transmission region different from the firsttransmission region to the MS using the UL-MAP message (VoIP_UL_IE)acting as a control message in S1002.

However, it should be noted that the above-mentioned UL-MAP message maybe lost or damaged during wired or wireless transmission in S1002, orthe MS may receive the UL-MAP message abnormally in S1002. According toanother embodiment of the present invention, the UL-MAP message has beenlost and the MS does not receive the UL-MAP message.

Even if the MS has not received the UL-MAP message, the BS can allocatethe second transmission region to the MS nonetheless in S1003. However,in S1003, the BS does not actually allocate the radio resource region tothe MS using the control message. The UL-MAP message used as the controlmessage is transmitted only when the transmission region needs to bechanged to another region.

Since the MS has not received the UL-MAP message in S1002, it is unableto transmit the VoIP packet in S1004. If the BS detects no signal in thesecond transmission region which has been assigned to the MS, itretransmits the UL-MAP message to the MS in order to reallocate thesecond transmission region to the MS in S1005.

Referring to FIG. 11, in a downlink, the VoIP service is generatedbetween the MS and the BS and the BS allocates the first transmissionregion for providing the MS with the VoIP service. The above-mentionedoperations are similar to S201˜S204 of FIG. 1, and therefore, the samesteps are omitted and only different steps are described with referenceto FIG. 11.

The BS assigns the first transmission region to the MS to transmit theVoIP packet and transmits the VoIP packet to the MS via the firsttransmission region in S1101. While the VoIP packet is communicatedbetween the MS and the BS, a first transmission region for providing acurrent VoIP service may need to be changed to a new second transmissionregion. In this case, the BS may allocate the second transmission regiondifferent from the first transmission region to the MS using the DL-MAPmessage (VoIP_DL_IE) acting as a control message in S1102.

However, it should be noted that the above-mentioned DL-MAP message maybe lost or damaged during wired or wireless transmission in S1102, orthe MS may receive the DL-MAP message abnormally in S1102. According toanother embodiment of the present invention, the DL-MAP message is lostand the MS receives no DL-MAP message.

Even if the MS receives no DL-MAP message and does not recognize thesecond transmission region as a new transmission region, the BS canallocate the second transmission region to the MS nonetheless in S1103.However, in S1103, the BS does not actually allocate the radio-resourceregion to the MS using the control message. The DL-MAP message used asthe control message is transmitted only when the transmission regionneeds to be changed to another region.

The BS transmits the VoIP packet to the MS via the allocated secondtransmission region in S1104. However, although the BS transmits theVoIP packet to the MS via the second transmission region in S1104, theMS has recognized the first transmission region as the VoIP-serviceregion. As a result, the MS is unable to receive the VoIP packet whichhas been transmitted to the second transmission region by the BS.

Therefore, the MS is unable to transmit the ACK signal for the VoIPpacket to the BS in S1105. The ACK signal of S1105 plays a unique rolewhich is different from those of FIGS. 4˜9. In other words, the ACKsignal in S1105 is equivalent to the ACK signal for the VoIP packet. TheACK signals of FIGS. 4˜9 are related to the ACK signals for the controlmessage. When the BS detects no signal in the second transmission regionwhich has been assigned to the MS, it retransmits the DL-MAP message tothe MS in order to reallocate the second transmission region to the MSin S1106.

As described above, FIGS. 4 to 11 have depicted various embodiments ofthe present invention. The above-mentioned methods proposed by the aboveembodiments can be applied not only to the above described embodimentsin which the radio resources are allocated, but also to the other casesin which the allocated resources are modified or deleted or newresources are continuously allocated.

The present invention has the following effects. First, although acontrol message for assigning the transmission region to provide theVoIP service is lost or has faulty or erroneous operations, the presentinvention can quickly retransmit the control message such that it cansolve the lost or damaged packet generated between the MS and the BS.

Second, the present invention can solve the problem encountered when atransmission region recognized by each MS is different from that of theBS in the uplink. That is, the present invention prevents the lost VoIPpacket encountered when the MS and the BS have recognized differenttransmission regions. Also, the MS has information of another regioninstead of a region assigned to the MS itself such that the collisionproblem encountered when another MS transmits the packet can be solved.

Third, although the control message for assigning the transmissionregion is damaged or lost, the present invention can immediatelyre-assign the transmission region. Therefore, the present invention cansolve the problem when the MS is unable to recognize the downlinktransmission region assigned from the BS.

Fourth, the present invention can reduce an amount of overhead of theMAP message to implement a periodic traffic pattern and a connection offixed-sized payload, for example, data information.

The above-mentioned messages and parameters are disclosed for onlyillustrative purposes of the present invention. If required, othermessages or other parameters may also be used to implement the samepurpose as that of the present invention. It should be noted that mostterminology disclosed in the present invention is defined inconsideration of functions of the present invention, and can bedifferently determined according to intention of those skilled in theart or usual practices. Therefore, it is preferable that theabove-mentioned terminology be understood on the basis of all contentsdisclosed in the present invention.

Although the preferred embodiments of the present invention weredisclosed for illustrative purposes, those skilled in the art willappreciate that various variations and modifications are possible,without departing from the scope and spirit of the invention asdisclosed in the accompanying claims. Thus, it is intended that thepresent invention cover the modifications and variations of thisinvention provided they come within the scope of the appended claims andtheir equivalents.

1. A method of allocating a radio resource in a wireless access system,the method comprising: receiving, by a mobile station, a first uplinkMAP message from a base station, the first uplink MAP message includinga first persistent uplink MAP information element, wherein the firstpersistent uplink MAP information element comprises first resourceallocation information for persistently allocating a first resourceallocation region for transmitting uplink data of the mobile station andfirst ACK information indicating a first ACK transmission region; andtransmitting, by the mobile station, an acknowledgment (ACK) message tothe base station via the first ACK transmission region when the mobilestation successfully receives the first persistent uplink MAPinformation element, wherein the first resource allocation informationincludes at least an orthogonal frequency division multiplexing access(OFDMA) symbol offset, a subchannel offset, or OFDMA slot informationwhich indicates the first resource allocation region.
 2. The method ofclaim 1, further comprising: transmitting the uplink data to the basestation by the mobile station via the assigned first resource allocationregion.
 3. The method of claim 1, wherein the base station retransmitsthe first uplink MAP message at a next frame of a frame where the firstuplink MAP message is transmitted if the ACK message is not receivedfrom the mobile station.
 4. The method of claim 1, wherein the basestation retransmits the first uplink MAP message after a predeterminednumber of frames if the ACK message is not received from the mobilestation.
 5. The method of claim 1, wherein the uplink data has aperiodic traffic pattern and a fixed payload size.
 6. The method ofclaim 1, wherein the uplink data comprises an IP-based Voice overInternet Protocol (VoIP) data.
 7. The method of claim 1, wherein thefirst persistent uplink MAP information element further comprises afield for indicating whether the first resource allocation region isallocated or de-allocated.
 8. A mobile station for supporting a methodof allocating a radio resource in a wireless access system, the mobilestation configured for: receiving a first uplink MAP message from a basestation, the first uplink MAP message including a first persistentuplink MAP information element, wherein the first persistent uplink MAPinformation element comprises first resource allocation information forpersistently allocating a first resource allocation region fortransmitting uplink data of the mobile station and first ACK informationindicating a first ACK transmission region; and transmitting anacknowledgment (ACK) message to the base station via the first ACKtransmission region when the first persistent uplink MAP informationelement is successfully received, wherein the first resource allocationinformation includes at least an orthogonal frequency divisionmultiplexing access (OFDMA) symbol offset, a subchannel offset, or OFDMAslot information which indicates the first resource allocation region.9. The mobile station of claim 8, wherein the mobile station is furtherconfigured for: transmitting the uplink data to the base station via theassigned first resource allocation region.
 10. The mobile station ofclaim 8, wherein the base station retransmits the first uplink MAPmessage at a next frame of a frame where the first uplink MAP message istransmitted if the ACK message is not received from the mobile station.11. The mobile station of claim 8, wherein the base station retransmitsthe first uplink MAP message after a predetermined number of frames ifthe ACK message is not received from the mobile station.
 12. The mobilestation of claim 8, wherein the uplink data has a periodic trafficpattern and a fixed payload size.
 13. The mobile station of claim 8,wherein the uplink data comprises an IP-based Voice over InternetProtocol (VoIP) data.
 14. The mobile station of claim 8, wherein thefirst persistent uplink MAP information element further comprises afield for indicating whether the first resource allocation region isallocated or de-allocated.